1. Field of the Invention
The present invention relates to a metal ion detecting device. More specifically, the present invention relates to a metal ion detecting device for detecting leakage of metal ions of sodium or the like which is used, for example, as a coolant for a fast breeder reactor.
2. Description of the Prior Art
Liquid sodium is used as a coolant in a fast breeder. When sodium leaks from the facilities or piping, it is brought into contact with ambient air or moisture to form a corrosive compound. If this leakage is left undetected, the facilities or piping are damaged even when the amount of the leaked sodium is small. This results in a secondary leakage of a larger scale. For this reason, it is necessary to detect leakage at an early stage irrespective of its scale and to take a proper countermeasure.
A conventional device for detecting leaked sodium ions is known which utilizes electrical conductivity of the leaked sodium. The conventional sodium detecting device is arranged in the vicinity of facilities or piping through which sodium flows and includes a trap for collecting the leaked sodium. A pair of electrodes is arranged at the bottom of the trap. The leaked sodium is collected by this trap to electrically conduct the electrodes, so that leakage of sodium is detected. However, this device does not operate until a considerable amount of sodium has leaked. Thus, it is difficult to detect leakage of sodium at an early stage.
Liquid sodium which has leaked to the outside reacts with air to generate white smoke. Therefore, a method for detecting leakage of sodium is known which detects the white smoke with a smoke detector. However, such a smoke detector tends to operate erroneously and has a low sensitivity since it may be operated by dust or other types of smoke than the white smoke.
Sodium which is used as a coolant in a fast breeder generally has induced radioactivity. Another method for detecting leakage of sodium is thus known which incorporates a radiation detector which is arranged near facilities or piping through which sodium flows and which detects leakage of radioactive sodium. However, the secondary coolant of the fast breeder generally has small radioactivity. Therefore, this method fails to detect leakage of sodium as the secondary coolant or sodium which is not radioactive.